Do you mean using 3D programs and doing postwork, or drawing from scratch in PS?

If it's from scratch, life-study and drawing courses would be your best start. Doesn't matter if it's on paper or pixels - knowing how to draw is your best base of understanding how to achieve what you want in your artwork.

Experiment with drawing from pictures of women - just draw what you see to figure out proportions and texture and lighting - there is no right or wrong, just your version of a finished image.
Does that make sense? I hope that helps-
-Lew ;-)